Set your Instant Pot to the sauté function. In a small dish, mix together the salt, pepper, garlic powder, onion powder, and smoked paprika. Coat the beef roast evenly with this seasoning blend, ensuring every side is covered.

Heat the oil in the Instant Pot for about 30 seconds, then carefully place the roast into the pot using tongs. Let it sear without moving for 3-4 minutes until a rich brown crust forms. Rotate the roast to sear the other sides, repeating this process until all sides are browned.

Switch the Instant Pot to the "pressure cook" setting on high. Set the timer for 60 minutes if your roast weighs 3 pounds or 80 minutes for a 5-pound roast (see notes for baby carrots). Arrange the potatoes, onions, and carrots around the roast. Pour in the beef broth and Worcestershire sauce, making sure to cover the vegetables and roast.

Secure the lid on the Instant Pot, ensuring it’s locked, and set the vent to the sealed position. Once cooking is complete, allow the pressure to release naturally for 10 minutes. Afterward, switch the vent to the venting position to release any remaining steam before opening the lid.

Transfer the roast, potatoes, onions, and carrots to a serving platter. Shred the roast into large chunks using two forks. Use a strainer to remove any solids from the broth remaining in the Instant Pot. Set the pot to the "soup" setting and bring the broth to a boil.

In a separate bowl, whisk together the cornstarch and water to form a slurry. Gradually stir this mixture into the boiling broth until it thickens into a rich gravy. Adjust the seasoning with additional salt, pepper, and garlic powder to taste.

Serve the roast and vegetables with the gravy drizzled generously over them. For a final touch, garnish with fresh thyme or parsley if desired.